The presence of OHSS is defined in accordance with the Golan 5 grade system and women who at least are at grade 2 of this classification (Mild) considered as OHSS cases and will experience abdominal distention and discomfort, nausea and vomiting and/or diarrhea and enlargement of ovaries(5-12cm). In Moderate forms, ultrasound evidences of ascites will be observed and severe OHSS accompany with clinical signs of ascites, hydrothorax, breathing disorders, hemoconcentration, coagulopathy and renal perfusion decrease.